I've got a choc lab, 9 years old, 115 Lbs and a great family and hunting dog. As far as home defense goes, he looks very intense and anytime someone new enters out house he will stand rock still until the front door closes. I think he's just waiting to make sure that they can't get away before he licks off 2 layers of skin and makes them pet him. He would probably help you unload the china hutch if you could agree on a daily belly rub. LOL.
All kidding aside, they are great dogs and the transition from the field to the house is transparent.
Mine doesn't know he's a dog and he has absolutely no idea he weighs as much as he does. They just want to make you happy.

My wife has issued the following law in our house.

1. If anything happens to the dog while we are hunting, I can't come home.